Saint Petersburg Dam - Floods On The Neva

Floods On The Neva

Saint Petersburg suffers from frequent floods (more than 340 in recorded history), some being natural disasters. It is situated on drained marshlands, isles and lowlands in the estuary of the Neva River, where flooding is common. Flow from Lake Ladoga is significant and the Neva's current is rapid, but flooding is generally caused by water backing up the Neva from its outlet, the Gulf of Finland. Most rivers flood in periods of exceptionally high flow, but the Neva typically floods in late autumn.

In the early literature, high winds from the Gulf of Finland were often cited as the cause of Neva flooding, but scientists now understand the more complex hydrometeorological chain of events behind it. A low-pressure region in the North Atlantic moves onshore, giving rise to cyclonic lows on the Baltic Sea. The low pressure of the cyclone draws greater-than-normal quantities of water into the virtually land-locked Baltic. As the cyclone continues inland, long low-frequency seiche waves are established in the Baltic. When the waves reach the narrow and shallow Neva Bay, they become much higher, ultimately breaching the Neva embankments.

The worst such flood occurred on 19 November 1824, when the water level rose 4.21 m (13.8 ft) above normal. The playwright Alexander Griboyedov wrote, "The embankments of the various canals had disappeared and all the canals had united into one. Hundred-year-old trees in the Summer Garden were ripped from the ground and lying in rows, roots upward." When the waters receded 569 people were dead, with thousands more injured or made ill – more than 300 buildings had been washed away. The 1824 inundation is the setting for Alexander Pushkin's famous poem, The Bronze Horseman (1834). Other disastrous floods took place in 1777 and 1924. One of the most recent floods occurred on 18–19 October 1998, when the water level rose to 2.2 m (7.2 ft).